Current transmission assembly for automatic transmission, a standard accessory in the modern vehicles, can provide normally 4 or 5 gear ratios between the prime mover and the driven wheels for building up the necessary torque while the vehicle moves from zero speed to the normal speed, and for over drive. The variable transmission systems currently in use, mostly rely upon conventional speed variators, such as steel chain with flexible pulley, toroidal drives, hydraulic torque convertors, electric generators etc. for transmitting the power, which primarily suffer from the delay for responding to load change, and also the limited capacity, and the inability to efficiently transmit the power, mainly due to the loss suffered by the conversion of mechanical power into pressure energy, electrical energy etc. There are also known “torque transfer systems” (Phelan) which can be used only for forward movement, in one configuration, and not for reverse and overdrive, which needs different configurations of gear elements. These systems can be used only for differential drives and produce excessive heat during normal operation wherein one of the hydraulic pumps will discharge against the other hydraulic pump, keeping both the pumps in a locked position having no torque differentiation. Additionally, these transmission systems are expensive and suffer from operational inefficiency such as delay for automatically correcting the torque level for different driving conditions, resulting in excessive fuel consumption, poor acceleration, dirty emission and high rate of wear.
The automatic transmission system for which an Indian patent and a U S patent has been granted to me, as mentioned earlier, eliminates the above deficiencies to a considerable extend. However the technology followed in this system for maintaining the speed of the planet carrier and sun gear at the same level during normal drive, by directing the fluid discharge from the right side hydraulic pump rotating with the sun gear, to the suction side of the left side hydraulic pump rotating with the planet carrier, can cause excessive heat during continuous operation and can waste pressure energy to certain extent. The fluid under pressure, discharged from these pumps to the fluid tank also wastes certain amount of pressure energy.